The ncurses library routines give the user a terminal-independent method
of updating character screens with reasonable optimization. This
implementation is ``new curses'' (ncurses) and is the approved replacement for
4.4BSD classic curses, which has been discontinued. This describes
ncurses version 5.7.

The ncurses library emulates the curses(3) library of System V
Release 4 UNIX, and XPG4 (X/Open Portability Guide) curses (also known as XSI
curses). XSI stands for X/Open System Interfaces Extension. The ncurses
library is freely redistributable in source form. Differences from the SVr4
curses are summarized under the EXTENSIONS and PORTABILITY
sections below and described in detail in the respective EXTENSIONS,
PORTABILITY and BUGS sections of individual man pages.

The ncurses library also provides many useful extensions, i.e., features
which cannot be implemented by a simple add-on library but which require
access to the internals of the library.

A program using these routines must be linked with the -lncurses option.

The library uses the locale which the calling program has initialized. That is
normally done with setlocale:

setlocale(LC_ALL, "");

If the locale is not initialized, the library assumes that characters are
printable as in ISO-8859-1, to work with certain legacy programs. You should
initialize the locale and not rely on specific details of the library when the
locale has not been setup.

The function initscr or newterm must be called to initialize the
library before any of the other routines that deal with windows and screens
are used. The routine endwin must be called before exiting.

To get character-at-a-time input without echoing (most interactive, screen
oriented programs want this), the following sequence should be used:

initscr(); cbreak(); noecho();

Most programs would additionally use the sequence:

nonl();intrflush(stdscr, FALSE);keypad(stdscr, TRUE);

Before a curses program is run, the tab stops of the terminal should be
set and its initialization strings, if defined, must be output. This can be
done by executing the tput init command after the shell environment
variable TERM has been exported. tset(1) is usually responsible
for doing this. [See terminfo(5) for further details.]

The ncurses library permits manipulation of data structures, called
windows, which can be thought of as two-dimensional arrays of
characters representing all or part of a CRT screen. A default window called
stdscr, which is the size of the terminal screen, is supplied. Others
may be created with newwin.

Note that curses does not handle overlapping windows, that's done by the
panel(3) library. This means that you can either use stdscr or
divide the screen into tiled windows and not using stdscr at all.
Mixing the two will result in unpredictable, and undesired, effects.

Windows are referred to by variables declared as WINDOW *. These data
structures are manipulated with routines described here and elsewhere in the
ncurses manual pages. Among those, the most basic routines are
move and addch. More general versions of these routines are
included with names beginning with w, allowing the user to specify a
window. The routines not beginning with w affect stdscr.

After using routines to manipulate a window, refresh is called, telling
curses to make the user's CRT screen look like stdscr. The
characters in a window are actually of type chtype, (character and
attribute data) so that other information about the character may also be
stored with each character.

Special windows called pads may also be manipulated. These are windows
which are not constrained to the size of the screen and whose contents need
not be completely displayed. See curs_pad(3) for more information.

In addition to drawing characters on the screen, video attributes and colors may
be supported, causing the characters to show up in such modes as underlined,
in reverse video, or in color on terminals that support such display
enhancements. Line drawing characters may be specified to be output. On input,
curses is also able to translate arrow and function keys that transmit
escape sequences into single values. The video attributes, line drawing
characters, and input values use names, defined in <curses.h>,
such as A_REVERSE, ACS_HLINE, and KEY_LEFT.

If the environment variables LINES and COLUMNS are set, or if the
program is executing in a window environment, line and column information in
the environment will override information read by terminfo. This would
affect a program running in an AT&T 630 layer, for example, where the size
of a screen is changeable (see ENVIRONMENT).

If the environment variable TERMINFO is defined, any program using
curses checks for a local terminal definition before checking in the
standard place. For example, if TERM is set to att4424, then the
compiled terminal definition is found in

/usr/share/terminfo/a/att4424.

(The a is copied from the first letter of att4424 to avoid
creation of huge directories.) However, if TERMINFO is set to
$HOME/myterms, curses first checks

$HOME/myterms/a/att4424,

and if that fails, it then checks

/usr/share/terminfo/a/att4424.

This is useful for developing experimental definitions or when write permission
in /usr/share/terminfo is not available.

The integer variables LINES and COLS are defined in
<curses.h> and will be filled in by initscr with the size
of the screen. The constants TRUE and FALSE have the values
1 and 0, respectively.

The curses routines also define the WINDOW * variable
curscr which is used for certain low-level operations like clearing and
redrawing a screen containing garbage. The curscr can be used in only a
few routines.

Many curses routines have two or more versions. The routines prefixed
with w require a window argument. The routines prefixed with p
require a pad argument. Those without a prefix generally use stdscr.

The routines prefixed with mv require a y and x coordinate
to move to before performing the appropriate action. The mv routines
imply a call to move before the call to the other routine. The
coordinate y always refers to the row (of the window), and x
always refers to the column. The upper left-hand corner is always (0,0), not
(1,1).

The routines prefixed with mvw take both a window argument and x
and y coordinates. The window argument is always specified before the
coordinates.

In each case, win is the window affected, and pad is the pad
affected; win and pad are always pointers to type WINDOW.

Option setting routines require a Boolean flag bf with the value
TRUE or FALSE; bf is always of type bool. Most of
the data types used in the library routines, such as WINDOW,
SCREEN, bool, and chtype are defined in
<curses.h>. Types used for the terminfo routines such as
TERMINAL are defined in <term.h>.

This manual page describes functions which may appear in any configuration of
the library. There are two common configurations of the library:

Attributes alone (no corresponding character) may be stored in
chtype or the equivalent attr_t data. In either case, the
data is stored in something like an integer.

Each cell (row and column) in a WINDOW is stored as a
chtype.

ncursesw

the so-called "wide" library, which handles multibyte
characters. The "wide" library includes all of the calls from
the "normal" library. It adds about one third more calls using
data types which store multibyte characters:

cchar_t

corresponds to chtype. However it is a structure, because more data
is stored than can fit into an integer. The characters are large enough to
require a full integer value - and there may be more than one character
per cell. The video attributes and color are stored in separate fields of
the structure.

Each cell (row and column) in a WINDOW is stored as a
cchar_t.

wchar_t

stores a "wide" character. Like chtype, this may be an
integer.

wint_t

stores a wchar_t or WEOF - not the same, though both may
have the same size.

The "wide" library provides new functions which are analogous to
functions in the "normal" library. There is a naming convention
which relates many of the normal/wide variants: a "_w" is
inserted into the name. For example, waddch becomes
wadd_wch.

Routines that return an integer return ERR upon failure and an integer
value other than ERR upon successful completion, unless otherwise noted
in the routine descriptions.

All macros return the value of the w version, except setscrreg,
wsetscrreg, getyx, getbegyx, and getmaxyx. The
return values of setscrreg, wsetscrreg, getyx,
getbegyx, and getmaxyx are undefined (i.e., these should not be
used as the right-hand side of assignment statements).

The following environment symbols are useful for customizing the runtime
behavior of the ncurses library. The most important ones have been
already discussed in detail.

BAUDRATE

The debugging library checks this environment symbol when the application
has redirected output to a file. The symbol's numeric value is used for
the baudrate. If no value is found, ncurses uses 9600. This allows
testers to construct repeatable test-cases that take into account costs
that depend on baudrate.

CC

When set, change occurrences of the command_character (i.e., the
cmdch capability) of the loaded terminfo entries to the value of
this symbol. Very few terminfo entries provide this feature.

COLUMNS

Specify the width of the screen in characters. Applications running in a
windowing environment usually are able to obtain the width of the window
in which they are executing. If neither the COLUMNS value nor the
terminal's screen size is available, ncurses uses the size which
may be specified in the terminfo database (i.e., the cols
capability).

It is important that your application use a correct size for the screen.
This is not always possible because your application may be running on a
host which does not honor NAWS (Negotiations About Window Size), or
because you are temporarily running as another user. However, setting
COLUMNS and/or LINES overrides the library's use of the
screen size obtained from the operating system.

Either COLUMNS or LINES symbols may be specified
independently. This is mainly useful to circumvent legacy misfeatures of
terminal descriptions, e.g., xterm which commonly specifies a 65 line
screen. For best results, lines and cols should not be
specified in a terminal description for terminals which are run as
emulations.

Use the use_env function to disable all use of external environment
(including system calls) to determine the screen size.

ESCDELAY

Specifies the total time, in milliseconds, for which ncurses will await a
character sequence, e.g., a function key. The default value, 1000
milliseconds, is enough for most uses. However, it is made a variable to
accommodate unusual applications.

The most common instance where you may wish to change this value is to
work with slow hosts, e.g., running on a network. If the host cannot read
characters rapidly enough, it will have the same effect as if the terminal
did not send characters rapidly enough. The library will still see a
timeout.

Note that xterm mouse events are built up from character sequences
received from the xterm. If your application makes heavy use of
multiple-clicking, you may wish to lengthen this default value because the
timeout applies to the composed multi-click event as well as the
individual clicks.

In addition to the environment variable, this implementation provides a
global variable with the same name. Portable applications should not rely
upon the presence of ESCDELAY in either form, but setting the environment
variable rather than the global variable does not create problems when
compiling an application.

HOME

Tells ncurses where your home directory is. That is where it may
read and write auxiliary terminal descriptions:

$HOME/.termcap

$HOME/.terminfo

LINES

Like COLUMNS, specify the height of the screen in characters. See COLUMNS
for a detailed description.

MOUSE_BUTTONS_123

This applies only to the OS/2 EMX port. It specifies the order of buttons
on the mouse. OS/2 numbers a 3-button mouse inconsistently from other
platforms:

1 = left

2 = right

3 = middle.

This symbol lets you customize the mouse. The symbol must be three numeric
digits 1-3 in any order, e.g., 123 or 321. If it is not specified,
ncurses uses 132.

NCURSES_ASSUMED_COLORS

Override the compiled-in assumption that the terminal's default colors are
white-on-black (see default_colors(3)). You may set the foreground
and background color values with this environment variable by proving a
2-element list: foreground,background. For example, to tell ncurses to not
assume anything about the colors, set this to "-1,-1". To make
it green-on-black, set it to "2,0". Any positive value from zero
to the terminfo max_colors value is allowed.

NCURSES_GPM_TERMS

This applies only to ncurses configured to use the GPM interface.

If present, the environment variable is a list of one or more terminal
names against which the TERM environment variable is matched. Setting it
to an empty value disables the GPM interface; using the built-in support
for xterm, etc.

If the environment variable is absent, ncurses will attempt to open GPM if
TERM contains "linux".

NCURSES_NO_HARD_TABS

Ncurses may use tabs as part of the cursor movement optimization.
In some cases, your terminal driver may not handle these properly. Set
this environment variable to disable the feature. You can also adjust your
stty settings to avoid the problem.

NCURSES_NO_MAGIC_COOKIES

Some terminals use a magic-cookie feature which requires special handling
to make highlighting and other video attributes display properly. You can
suppress the highlighting entirely for these terminals by setting this
environment variable.

NCURSES_NO_PADDING

Most of the terminal descriptions in the terminfo database are written for
real "hardware" terminals. Many people use terminal emulators
which run in a windowing environment and use curses-based applications.
Terminal emulators can duplicate all of the important aspects of a
hardware terminal, but they do not have the same limitations. The chief
limitation of a hardware terminal from the standpoint of your application
is the management of dataflow, i.e., timing. Unless a hardware terminal is
interfaced into a terminal concentrator (which does flow control), it (or
your application) must manage dataflow, preventing overruns. The cheapest
solution (no hardware cost) is for your program to do this by pausing
after operations that the terminal does slowly, such as clearing the
display.

As a result, many terminal descriptions (including the vt100) have delay
times embedded. You may wish to use these descriptions, but not want to
pay the performance penalty.

Set the NCURSES_NO_PADDING symbol to disable all but mandatory padding.
Mandatory padding is used as a part of special control sequences such as
flash.

NCURSES_NO_SETBUF

Normally ncurses enables buffered output during terminal
initialization. This is done (as in SVr4 curses) for performance reasons.
For testing purposes, both of ncurses and certain applications,
this feature is made optional. Setting the NCURSES_NO_SETBUF variable
disables output buffering, leaving the output in the original (usually
line buffered) mode.

NCURSES_NO_UTF8_ACS

During initialization, the ncurses library checks for special cases
where VT100 line-drawing (and the corresponding alternate character set
capabilities) described in the terminfo are known to be missing.
Specifically, when running in a UTF-8 locale, the Linux console emulator
and the GNU screen program ignore these. Ncurses checks the TERM
environment variable for these. For other special cases, you should set
this environment variable. Doing this tells ncurses to use Unicode values
which correspond to the VT100 line-drawing glyphs. That works for the
special cases cited, and is likely to work for terminal emulators.

When setting this variable, you should set it to a nonzero value. Setting
it to zero (or to a nonnumber) disables the special check for Linux and
screen.

NCURSES_TRACE

During initialization, the ncurses debugging library checks the
NCURSES_TRACE symbol. If it is defined, to a numeric value, ncurses
calls the trace function, using that value as the argument.

The argument values, which are defined in curses.h, provide several
types of information. When running with traces enabled, your application
will write the file trace to the current directory.

TERM

Denotes your terminal type. Each terminal type is distinct, though many
are similar.

TERMCAP

If the ncurses library has been configured with termcap
support, ncurses will check for a terminal's description in termcap
form if it is not available in the terminfo database.

The TERMCAP symbol contains either a terminal description (with newlines
stripped out), or a file name telling where the information denoted by the
TERM symbol exists. In either case, setting it directs ncurses to
ignore the usual place for this information, e.g., /etc/termcap.

TERMINFO

Overrides the directory in which ncurses searches for your terminal
description. This is the simplest, but not the only way to change the list
of directories. The complete list of directories in order follows:

-

the last directory to which ncurses wrote, if any, is searched
first

-

the directory specified by the TERMINFO symbol

-

$HOME/.terminfo

-

directories listed in the TERMINFO_DIRS symbol

-

one or more directories whose names are configured and compiled into the
ncurses library, e.g., /usr/share/terminfo

TERMINFO_DIRS

Specifies a list of directories to search for terminal descriptions. The
list is separated by colons (i.e., ":") on Unix, semicolons on
OS/2 EMX. All of the terminal descriptions are in terminfo form, which
makes a subdirectory named for the first letter of the terminal names
therein.

TERMPATH

If TERMCAP does not hold a file name then ncurses checks the
TERMPATH symbol. This is a list of filenames separated by spaces or colons
(i.e., ":") on Unix, semicolons on OS/2 EMX. If the TERMPATH
symbol is not set, ncurses looks in the files /etc/termcap,
/usr/share/misc/termcap and $HOME/.termcap, in that order.

The library may be configured to disregard the following variables when the
current user is the superuser (root), or if the application uses setuid or
setgid permissions: $TERMINFO, $TERMINFO_DIRS, $TERMPATH, as well as $HOME.

The ncurses library can be compiled with an option (-DUSE_GETCAP)
that falls back to the old-style /etc/termcap file if the terminal setup code
cannot find a terminfo entry corresponding to TERM. Use of this feature
is not recommended, as it essentially includes an entire termcap compiler in
the ncurses startup code, at significant cost in core and startup
cycles.

The ncurses library includes facilities for capturing mouse events on
certain terminals (including xterm). See the curs_mouse(3) manual page
for details.

The ncurses library includes facilities for responding to window resizing
events, e.g., when running in an xterm. See the resizeterm(3) and
wresize(3) manual pages for details. In addition, the library may be
configured with a SIGWINCH handler.

The ncurses library extends the fixed set of function key capabilities of
terminals by allowing the application designer to define additional key
sequences at runtime. See the define_key(3) key_defined(3), and
keyok(3) manual pages for details.

The ncurses library can exploit the capabilities of terminals which
implement the ISO-6429 SGR 39 and SGR 49 controls, which allow an application
to reset the terminal to its original foreground and background colors. From
the users' perspective, the application is able to draw colored text on a
background whose color is set independently, providing better control over
color contrasts. See the default_colors(3) manual page for details.

The ncurses library includes a function for directing application output
to a printer attached to the terminal device. See the curs_print(3)
manual page for details.

The ncurses library is intended to be BASE-level conformant with XSI
Curses. The EXTENDED XSI Curses functionality (including color support) is
supported.

A small number of local differences (that is, individual differences between the
XSI Curses and ncurses calls) are described in PORTABILITY
sections of the library man pages.

This implementation also contains several extensions:

The routine has_key is not part of XPG4, nor is it present in SVr4. See
the curs_getch(3) manual page for details.

The routine slk_attr is not part of XPG4, nor is it present in SVr4. See
the curs_slk(3) manual page for details.

The routines getmouse, mousemask, ungetmouse,
mouseinterval, and wenclose relating to mouse interfacing are
not part of XPG4, nor are they present in SVr4. See the curs_mouse(3)
manual page for details.

The routine mcprint was not present in any previous curses
implementation. See the curs_print(3) manual page for details.

The routine wresize is not part of XPG4, nor is it present in SVr4. See
the wresize(3) manual page for details.

The WINDOW structure's internal details can be hidden from application programs.
See curs_opaque(3) for the discussion of is_scrollok, etc.

In historic curses versions, delays embedded in the capabilities cr,
ind, cub1, ff and tab activated corresponding
delay bits in the UNIX tty driver. In this implementation, all padding is done
by sending NUL bytes. This method is slightly more expensive, but narrows the
interface to the UNIX kernel significantly and increases the package's
portability correspondingly.

The header file <curses.h> automatically includes the header files
<stdio.h> and <unctrl.h>.

If standard output from a ncurses program is re-directed to something
which is not a tty, screen updates will be directed to standard error. This
was an undocumented feature of AT&T System V Release 3 curses.